A person writes a letter to four of his friends. He asks each one of them to copy the letter and mail to four different persons with instruction that they move the chain similarly. Assuming that the chain is not broken and that it costs 50 paise

Answer

N/a

Explanation

First friend writes 4 letters.
These four persons write four-four letters.
`therefore "Number of letters written at 2nd stage "=4xx4=16`
Similarly, number of letters written at 3rd stage `=16xx4=64`
Sequence formed : 4, 16, 64,…
It is a G.P.
`"Here "a=4, r=(16)/(4)=4, n=8`
`therefore" "S=(a(r^(n)-1))/(r-1)=(4(4^(8)-1))/(4-r)=87380`
total postage at the rate of 50 p per letter
`=0.50xx87380=Rs 43690`